Fluid flow and heat transfer in regenerative cooling channels of rocket nozzles is a challenging research problem owing to its physical and geometrical complexities. Convergent–divergent rocket nozzles realize a varying wall heat transfer profile with a peak at its throat region. This creates an inherent difficulty in designing a proper single counter-current regenerative coolant path to maintain the nozzle wall within safe temperature limits during operation. Regenerative coolant channels with convex and concave lateral curvature improve heat transfer in the throat region of the nozzle compared to its parent counterpart without curvature. Secondary flow structures are formed due to the lateral curvature of the coolant fluid passages and are found to enhance the heat transfer considerably. The amplitude of lateral curvature plays a decisive role in thermo-hydraulic performance. More than a 20% increase in the average Nusselt number is possible by providing the double curvature to the coolant channel. The major advantage of a doubly curved coolant channel is that it provides effective wall cooling for a wider extent near the throat than other geometrical configurations